The development of thermotolerance in hyperthermal injury to the villus compartment of mouse small intestine.

The development and decay of thermotolerance in the villus compartment of the intestinal mucosa of mouse was investigated by giving a primary treatment of 41.5 degrees C for 1 hour (subthreshold for thermal injury) at various intervals before a second, test treatment of 43.0 degrees C for 30 min. The test treatment was given 65 hours after an intraperitoneal injection of 3H-thymidine (i.e. at a time when the heavily labelled cells could be seen to have moved from the crypts on to the upper halves of the villi) and thermal damage assessed by loss of radioactive label. A transient tolerance to the second treatment was induced by the primary treatment. This 'thermotolerance' was maximal 3-13 hours after the first treatment and had decayed by 24 hours. Both the extent and time course of expression and decay of thermotolerance in this post-mitotic functional compartment were very similar to those previously reported for damage to the proliferative epithelium as assayed by crypt loss. This suggests either that the kinetics of thermotolerance are not dependent on the proliferative status of the tissue or that there is a common limiting factor in thermotolerance development, despite the apparent difference between the two mucosal compartments in their susceptibilities to thermal injury.